Analytical Electron Microscopy of W-Core β-SiC Fibers for Use in an SiC-Based Composite Material for Fusion Applications

Abstract In this work, the interactions between tungsten (W) and silicon carbide (SiC) in Sigma^TM SiC fibers at high temperatures were characterized using scanning and transmission electron microscopy. These fibers could have the potential for use in fusion-related applications owing to their high thermal conductivity compared with pure SiC-based fibers. The as-received fibers were composed of a 100-μm-thick shell of radially textured β-SiC grains and a 15-μm-thick tungsten core, composed of a few hundreds of nm-sized elongated tungsten grains. The interfaces between the tungsten and the SiC and the SiC and the outer coatings were sharp and smooth. After heat treatment at 1,600°C for 3 h in Ar, the tungsten core reacted with SiC to form a rough interface surface. Inside the core, W₅Si₃, W₃Si, and W₂C phases were detected using energy-dispersive X-ray spectroscopy and electron-diffraction techniques. The mechanical properties of the fibers deteriorate after the heat treatment.